Every room for the drying of articles or materials, which will give off explosives or flammable vapors during the drying process, shall have an enclosure of two-hour fire-resistive construction, if it has a floor area of 1,000 square feet or less and of three-hour fire- resistive construction of solid masonry or concrete if it has a floor area exceeding 1,000 square feet but not more than 2,000 square feet; and of four-hour fire-resistive construction if it has a floor area exceeding 2,000 square feet; provided, however, that an opening, or openings from any adjoining room for a conveyor may be provided in an enclosure for any such drying room if each such adjoining room is made to conform with the requirements of this section for such a drying room; and provided further, that if a system of collecting and disposing of the vapors produced in the drying room is provided, then the enclosure for the drying room shall be not less than one-hour fire- resistive construction in any case, and the provisions of this section for an adjoining room in which there is a conveyor extending into the drying room shall not apply.
(Prior code § 129.1-75)